For producing hot drinks and beverages, such as for example coffee, tea, vegetable based infusions and the like, single dose packaging in the form of so-called capsules or pods are often used. Herein after the term capsule will be used to designate any such single dose packaging, including rigid or soft cartridges, pods or capsules, both gas tight or perforated. It shall be understood that, unless specifically indicated, the term encompasses any kind of single dose packaging suitable for preparing beverages by extraction using hot and possibly pressurized water. A single dose packaging can include sufficient ingredients to prepare more than just one portion beverage, for instance two portions. The term beverage as used herein designates any edible, mainly liquid or semi-liquid product.
Some known beverage producing machines comprise a brewing chamber having at least a first brewing chamber portion and a second brewing chamber portion, which are movable one with respect to the other for receiving a capsule therebetween and sealingly closing the capsule in the brewing chamber. Once the brewing chamber is closed, hot and possibly pressurized water is caused to pass through the brewing chamber and the capsule retained therein. The hot water extracts the ingredients contained in the capsule, producing the hot beverage.
In some beverage producing machines opening and closing of the brewing chamber is performed manually by means of a lever. Other known beverage producing machines are comprised of a hydraulic mechanism for opening and closing the brewing chamber.
For instance US 2013/0112084 discloses a beverage producing machine wherein a pump supplies cold water to a hydraulic piston-cylinder actuator, which opens and closes the brewing chamber. The same pump supplies additional water through a water heater, wherefrom hot water is then dispensed through a pressure regulating valve in the brewing chamber. A capsule can be arranged in the brewing chamber for receiving hot water and dispensing the beverage extracted from the ingredients contained therein by the hot water.
WO2012/049596 discloses a further coffee producing machine, having a hydraulic opening and closing mechanism. The pump provides hot water to the brewing chamber and cold water to a piston-cylinder actuator, which closes and maintains the brewing chamber in the closed position during brewing.
WO-A-02/058523 discloses a brewing unit comprising a brewing chamber having at least a first brewing chamber portion and a second brewing chamber portion, movable one with respect to the other, configured and arranged to take an open position and a closed brewing position. A hydraulic actuator is provided, for controlling the closing and opening movement of the brewing chamber. A water pump is further provided, which is fluidly connected to the brewing chamber through a first water path and further fluidly connected to the hydraulic actuator through a second water path, such that the pump can deliver pressurized water to the brewing chamber and to the hydraulic actuator, respectively. A water heater is arranged along the first water path. A first valve is positioned along the first water path and a second valve is positioned along the second water path, between the water pump and the hydraulic actuator. The first valve comprises a shutter and a spring and is calibrated to open when the water pressure in the first water path achieves a pre-set pressure value. The second valve is an electro-valve which is selectively switched between a first position and a second position. In the first position the second valve fluidly connects the hydraulic actuator to the pump and the first water path. In the second position the second valve fluidly connects the hydraulic actuator with a water return line, through which cold water from the hydraulic actuator is returned to a water tank. When a brewing cycle is performed, the second valve is switched in the first position and the pump starts pumping water in the second water path. The first valve remains closed until the pressure in the first and second water paths achieves the per-set pressure at which the first valve opens. When the first valve opens, water flows through the brewing chamber. The second valve remains open such that the same water pressure is present in both the first and second water paths. The closure pressure of the hydraulic actuator is thus set by the opening pressure of the first valve.
In these known machines having a hydraulic closing mechanism, presurized, hot water is dispensed through the brewing chamber; the pressure must be sufficient to enable the hydraulic actuator to safely maintain the brewing chamber in the closed position, while hot water flows therethrough.
These known devices, therefore, suffer from some limitations concerning the selectable pressure at which the beverage can be extracted, which is determined by the closure pressure. The extraction pressure affects the organoleptic characteristics of the beverage and thus the final result of the brewing process.
A need therefore exists, to further improve these known machines, to overcome or at least alleviate one or more of the limitations of the known machines.